1. Field of The Invention
The field of the present invention relates generally to hazardous waste management, and more particularly to the management of radioactive waste materials.
2. Discussion of Related Art
The management of hazardous waste material, including radioactive, biological, and chemical waste, is of critical concern to maintaining a safe environment. The management of such waste is multifaceted. An initial concern is to insure a high level of safety in handling these wastes at any given time. As such waste material is produced at a given site, the first concern is the containment of such hazardous waste products or material. As the secured waste material accumulates at a given site, the next concern is to transport the material away from the site in approved shipping containers, for delivery to a specialized facility for either storage and/or processing. Typically, high-level nuclear waste material produced at nuclear utility sites must be locally secured for a period of about 10 to 20 years. Thereafter, the radioactive waste material is planned to be transported to a specialized facility for longer term storage, and/or waste processing. In such intermediate term storage facilities nuclear waste may be stored in containers for 40 to 100 years, with the contents being accessible, which requires that the high-level nuclear waste must be retrievable and inspectable. After the passage of the intermediate storage time, the nuclear waste material may be processed or transported to other specialized sites for long term storage, for periods ranging from 300 to 1,000 years, for example. One such long term storage site is currently planned for the Tuff Repository in Nevada. As previously indicated, the management of hazardous waste material is not limited to radioactive waste, and similar concerns are associated with the management of biological and chemical waste. For chemical and biological wastes, the hazardous material may be processed, and rendered benign while in the container. However, radioactive waste management is particularly difficult in view of certain nuclear waste materials retaining high levels of radio activity for thousands of years.
Over the past 40 years there has been increasing concern and activity in providing appropriate containers and inspection apparatus for the storage of hazardous waste, particularly nuclear waste material. Recently, a number of articles have been published describing present activities in these areas. One article by T. W. Doering and D. Stahl, entitled "High Level Nuclear Waste Retrievability", appeared in The Proceedings of The Third International Conference on High Level Radioactive Waste Management, Apr. 12-16, 1992, pages 362-365, and describes a design of waste packages for deep geologic disposal of spent nuclear fuel, and high-level waste glass. The inspectability of such waste packages is also discussed.
In another article by D. Peters, K. Kundig, and D. Medley, entitled "Multi-Barrier, Copper-Base Containers for HLW Disposal", from The Proceedings of The Third International Conference on High Level Radioactive Waste Management, Apr. 12-16, 1992, pages 366-376, the use of copper and aluminum bronze for such containers is discussed. Various types of containers using such materials are also shown and described. The use of copper for various portions of such containers is emphasized.
Another article by K. Janberg, H. Spilker, and R. Huggenberg, entitled "The German Cask-Concept for Intermediate and Final Storage of Spent Fuel", from The Proceedings of The Third International Conference on High Level Radioactive Waste Management, Apr. 12-16, 1992, pages 385-394, shows and describes various designs for canisters for use in storing radioactive material. The basic design includes a final disposal cask or canister stored within an outer shielding cask or canister. Each canister is provided with its own lid.
Over the past 40 years many U.S. patents have been obtained for various container designs for storing nuclear waste. A number of such patents are discussed immediately below.
Dougherty, U.S. Pat. No. 2,758,367, shows a down welding process for welding closure caps to cylindrical containers. The cylindrical containers are oriented on a lathe-like device, with the longitudinal access of the container being parallel to the horizontal plane. A welding head is positioned proximate a circumferential groove for receiving a welding bead, with the welding head being above the cylinder and groove for providing down welding. As the cylinder is rotated the welding head is operated for causing a weld bead to be formed within the circumferential groove.
Lloyd et al., U.S. Pat. No. 3,327,892, shows a stainless steel tubular container for storing nuclear material. The end of the container is sealed via a cup-shaped lid 2. The upper circumferential edge of the cup lid 2 is welded via a circumferential weld 7 to the top edge of the container 1. Copper brazing is used to seal the sides of the cup lid 2 to opposing sides of the container 1.
Sannipoli, U.S. Pat. No. 3,734,387, teaches a tank fabrication system, whereby individual sections of a large cylindrical tank are oriented with their longitudinal axes parallel to the horizontal plane, and placed upon movable trollies. Apparatus is shown for rotating two sections to be joined for permitting welding thereof via a welding head positioned above the intersection between the two sections.
Eroshkin et al., U.S. Pat. No. 4,187,410, teaches a method for joining two pieces of metal together through use of a multi-pass welding bead within a narrow groove formed between the pieces.
Gesser et al, U.S. Pat. No. 4,320,847, shows a container for storing spent fuel elements that is substantially cylindrical in its main lower portion and has an uppermost portion that has diverging walls. A cup-like lid is fitted within the uppermost portion of the outwardly flaring wall members for sealing the container. The cup-like cap is welded about its circumferential lip to the interior wall portion of the frusto conical widening at the upper portion of the container.
Janberg, U.S. Pat. No. 4,508,969, shows a cylindrical container for storing spent reactor fuel elements. The container is closed off by a dome shaped lid or top member. The material for the container is indicated as being carbon steel or high-grade steel where thinner walls can be used. The outer portion of the container is a shielding layer made of polyethylene or some other hydrocarbon for absorbing residual neutron radiation.
Popp et al. U.S. Pat. No. 4,527,065, shows a storage container for the long term storage of radioactive material. The container is made from material such as cast iron and cast steel. A relatively flat cap or cover 6 is shaped to provide a circumferential weld groove between the bottom portion of the cap and the top lip of the container for permitting the cap to be welded to the container.
Popp et al., U.S. Pat. No. 4,572,959, shows a container for the long term storage of radioactive waste. The container is cylindrical and includes in the topmost portion a circular recess for receiving a closure cap or plug 4. A circumferential welding groove is formed between a beveled upper portion of the cap and a beveled or sloping interior topmost rim portion of the container, for receiving a weld bead. The container includes an interior base portion of cast iron, an outer wall layer 3 made of high-alloy austenitic nodular cast iron, and an interior cover 5 is fitted below the top cap 4.
Popp, U.S. Pat. No. 4,596,688, shows a container for the long term storage of radioactive materials that is made of steel, cast steel or similar material. The container is multilayered and substantially cylindrical in shape. The open top end is sealed by a multilayered cap which is shaped to form a circumferential groove with the top lip of the container for receiving a weld bead. Protective layers of the container are made of graphite, ceramic material or an enamel material.
Warder et al., U.S. Pat. No. 4,872,563, shows a container for storing hazardous materials. The container is particularly designed for storing biological materials.
Gaudin, U.S. Pat. No. 4,881,678, shows a robotic welding system that is remotely controlled. The system employs a welding process for applying a weld bead in multiple passes into a groove between two parts to be joined.
Madle et al. U.S. Pat. No. 4,976,912, teaches an apparatus for welding and testing a weld on a cover for sealing a container storing radioactive material. The system provides for mounting the container vertically on a rotatable platform. The system further includes a bridge-like arrangement for retaining welding tools in a fixed position for welding the cap to the top of the container as the container is rotated. Inspection tools are also located on the bridge in a fixed container for permitting inspection of the weld as the container is rotated.
Leebl, et al., U.S. Pat. No. 3,754,141, shows a storage container for radioactive material. The container is cylindrical and is provided with a shallow cup-like cap or lid. The container actually includes multiple containers surrounding one another.
Backus, U.S. Pat. No. 3,770,964, shows a container for storing radioactive material. This container shows a pair of annular seals 32 disposed within circular grooves for sealing a bottom portion of a cap to an interior ledge-like lip portion of the container.
Bock et al., U.S. Pat. No. 4,078,811, shows a sealing device that includes an elastic circumferential seal 3 for sealing a lid to the top of a container.
Baatz et al., U.S. Pat. No. 4,274,007, shows the use of a plurality of a "O"-ring seals between a step-shaped lid member and the interior step-like ledge and side portions of the upper portion of a storage container. The "O"-rings are contained within annular grooves.
Baatz et al. U.S. Pat. No. 4,445,042, shows a cylindrical container for radioactive waste that shows the use of metal "O"-rings, metal, elastomeric "O"-rings, and metal-to-metal seals, for sealing a converging step-like lid to a diverging stepped interior upper portion of the container.
Fields, U.S. Pat. No. 4,535,250, shows a container for radioactive material including silicone rubber seals 20, 29 and 31 for sealing a lid to the top of the container.
Popp et al., U.S. Pat. No. 4,594,214, shows a container for storing radioactive materials that includes a plurality of concentric layers or containers within a container. The innermost container is sealed by a screwed in cap. An intermediate portion of the container is sealed via a cup-like cap welded to an upper lip of the outer container via a topmost circumferential welding groove between the cap and interior side edge of the outer container. An outermost cap is screwed onto the top of the container.
Schroeder et al., U.S. Pat. No. 4,673,814, shows a cylindrical container for storing radioactive material. The container includes an interior uppermost diverging wall portion for receiving a cap member having outwardly diverging sides. The cap is welded via a weld groove to an interior portion of the uppermost wall of the container.
Koester et al, U.S. Pat. No. 4,702,391, disclose a corrosion resistant container for radioactive material. The container is lined with titanium-palladium alloy applied by explosion plating. Electron beam welding is used to close seams in the container. The bottom and cover lid of the container are apparently made of steel plates covered with a corrosion protected layer of titanium-palladium alloy applied by explosion plating. A circumferential weld is used about the bottom and top portions of the container. A cover plate 6 is used to cap off the container.
Bienek et al, U.S. Pat. No. 4,738,388, shows a container for storing radioactive material. The container is cylindrically shaped. A dual element cap mechanism is used for closing off the container. The cap includes metal-to-metal sealing, and is provided with a main first member that screws into the interior upper portion of the container, and forms a topmost circumferential groove 17 with the inside edge of the top portion thereof for receiving a weld bead.
Popp et al., U.S. Pat. No. 4,818,878, shows a double container for storing radioactive material. Several different embodiments are disclosed for sealing the top of the container through use of different capping mechanisms. Metal sealing rings are disclosed, as are the use of circumferential welding grooves for receiving a weld for sealing capping members to the container.
Madle et al., U.S. Pat. No. 4,847,009, shows a container for storing radioactive material that includes an inner container provided with a dome lid 8. The inner container is contained within an intermediate container that also is sealed at its top end with a dome lid 12.
McDaniels, Jr., U.S. Pat. No. 4,883,637, shows a closure arrangement for a container containing radioactive waste. "O"-ring seals 31 are used for sealing off one portion of a cap 26 to an interior flange or lip in an upper portion of a container.
Takeshima et al., U.S. Pat. No. 5,015,863, shows the use of shielding material for shielding nuclear waste containers. Composite particles are used to form the radiation shield from a group of materials including, but not limited to, oxides of beryllium, beryllium alloys, copper, copper alloys, and so forth.